Endothermic & Exothermic Chemical Reactions

Classifying Reactions

Reactions can be classified based on whether the change involves an absorption of energy or a release of energy .

These reactions are termed:1. Endothermic2. Exothermic

Endothermic Reactions A reaction in which energy is

absorbed from the surrounding environment as the products form

Molecules, atoms and bonds gain or energy from their surroundings.

The container in which an endothermic reaction is taking place will feel cold.

Exothermic Reactions Reaction in which energy is

released by the system into the surrounding environment as products form.

Molecules, atoms and bonds lose energy to their surroundings.

The container in which an exothermic reaction is taking place will feel warm.

Exothermic Reactions - Examples Sodium metal dropped into a

beaker of water causes an explosion.

Sweat beads form on your forehead after a heavy workout.

Cellular Respiration The freezing of a substance. Glow Sticks Fireworks Condensation

Endothermic Reactions - Examples Ice melts on a counter top. Green plants need sunlight

for growth (Photosynthesis)

Cold packs